The present invention relates to a vibration dampening laminate, and particularly a vibration dampening laminate for use in a vehicle interior.
Soundproofing in vehicles, particularly consumer automobiles and trucks, is a primary concern of automakers inasmuch as xe2x80x9cquietxe2x80x9d cars have become more and more popular. Conventionally, sound insulation pads are placed on surfaces of the bodywork, for example, on the floor, in the roof, on the fire wall and the like. The intent of the insulation pad is to deaden sounds and lessen vibration that are caused by movement of the vehicle, engine operation and any moving parts.
In general, soundproofing can be broken down into sound insulation, sound absorption, vibration dampening and vibration insulation. Sound insulation is typically accomplished by intercepting sound waves on the way of their transmission so that a transmitted sound level is made smaller than an initial sound level. Materials capable of reducing the sound energy are usable as a sound insulating material whose characteristics are determined by surface density, rigidity in bending and internal loss. In a given frequency region, a larger weight results in a higher sound insulating effect. Thus it is known to use high density resin mixtures in which large amounts of metallic powder, calcium carbonate, glass fibers or other fillers are incorporated. It is also konwn to impregnate a foamed material with asphalt such as described in Japanese patent application laid-open No. 18538/1986.
Sound absorption is accomplished by an absorption of vibration energy of sound as a heat energy by utilizing the viscosity resistance or frictional resistance of a high void material so that reflection of sound waves is made small. Examples of such materials include open cell foamed plastics, fiberglass, asbestos, and the like.
The vibration damping is typically accomplished by absorbing the energy of vibrations or sounds transmitted through material as a heat energy converted as a result of deformation in shear or compression of the material. The vibration damping material should favorably have a high loss coefficient and a high modulus of elasticity. The vibration damping material is usually used after attachment to or coating on vibrating plates. Two types of the damping are known including a restriction type where a panel is attached on the vibration damping material and a non-restriction type where no panel is used. Typical of the restriction type are vibration-damping steel sheets or plates of various types. Other vibration damping materials include resins in which large amounts of particles such as ferrites, metals, ceramics, various flakes such as talc, mica and the like, and various fibers such as wollastonite and glass fibers are included.
Although such techniques are known there remains a demand for improvement in the areas of sound deadening and vibration dampening. Moreover, the need for such techniques to be lightweight without being unduly expensive has become critical.
To this end, the present invention provides a vibration dampening laminate that is lightweight and has superior sound insulation and vibration dampening properties. The vibration dampening laminate comprises a foil constraining layer, a viscoelastic layer, a foam spacing layer and a pressure sensitive adhesive layer including a release layer. The pressure sensitive adhesive layer and release layer are contoured to fit a profile of the article being soundproofed and vibration dampened such as a floorpan of a vehicle interior. A decorative fabric layer may be placed on or bonded to the foil constraining layer. A particularly suitable fabric layer is a backed or unbacked carpet layer. The overall weight of the laminate is low, and 20 to 30 pounds can be reduced from the overall weight of the vehicle as compared to conventional means for sound deadening and vibration dampening.